Recent studies have revealed the existence of two new collagen chains, designated the A chain and B chain. The molecular organization of these chains is not entirely clear nor has their precise location within vertebrate tissues been established. Biochemically the chains display compositional features which prohibit their classification as either interstitial or basement-membrane collagen chains. Immunohistochemical techniques indicate that these chains are likely to be associated with the plasma membrane and may comprise part of an external cytoskeleton. Further evidence for this hypothesis is the fact that murine epithelial cells which apparently synthesize AB collagen exclusively, show a cessation of cell motility when collagen synthesis is disrupted by the proline analog L-azetidine-2-carboxylic acid. The present proposal is intended to make an in depth study of the synthesis secretion, and extracellular localization of these chains using cell culture techniques; investigate the collagen-plasma membrane interaction by fractionation of cells on density gradients to isolate pure plasma membranes; and evaluate the role of AB collagen in development and differentiation by examining its effectiveness as a cell culture substrate and its appearance and localization in the developing embryo.